Filter presses are well known and extensively utilized for separating solids from slurries. Such presses employ a plurality of filter plates which are held in contacting relationship between fixed and movable head members while the slurry is pumped into and through the press for collecting the solid in the form of filtrate or cake between adjacent filter plates. When the press is full, then the movable head is backed away from the plates into an open position, and thereafter the plates are individually and sequentially moved into an open position adjacent the movable head to permit discharge of the cake which has collected between the adjacent plates. To permit movement of the plates into an open position, numerous plate shifting mechanism have been provided on presses for permitting either automatic or manual control over the plate movement and cake discharge.
In one known press as manufactured and sold by the Assignee hereof, the plate shifter assembly is manually controlled by a press operator. The shifter assembly employs a downwardly-opening arch-shaped shifter housing which spans the top of the plates and has housing parts movably supported adjacent opposite sides of the press, which housing parts have shifter units mounted thereon. The complete shifter assembly is initially manually rollingly moved longitudinally along the press by the operator until the housing is positioned over the row of filter plates, and the operator precisely positions the assembly so that the plate shifting blades are aligned with the spaces between the handles of the endmost and next adjacent plates. When reaching this position, the operator stops the manual movement of the housing and then activates a control valve which in turn activates pressure cylinders associated with the shifter units. This causes the shifter blades to move upwardly between the handles, and then further cylinders are energized to cause the shifter blades to extend outwardly and engage the handles of the endmost plate to thus push the endmost plate toward and substantially into contact with the movable head. After the plate has been shifted to the opened position, and the cake discharged from between the two opened plates, then the operator again activates the control valve into a reversing position so that the shifter units are retracted and lowered into their original positions. The operator then manually moves the shifter housing until the shifter blades are aligned with the spaces between the next adjacent pair of plate handles, and the cycle is again repeated. This cycle is repeated until all of plates have been shifted so as to permit discharge of the cake. This entire cycle is almost wholly manually controlled, requiring constant manual supervision and manipulation, and hence does not provide efficient and time-saving discharge of the press, particularly due to the required utilization of manpower.
To overcome the required manual manipulations required for operation of presses of the type described above, other filter presses have been developed which incorporate shifting assemblies for permitting automatic sequential shifting and opening of the filter plates to permit cake discharge. Such assemblies traditionally employ shifter mechanisms positioned adjacent opposite sides of the press, and such shifter mechanisms necessarily employ drive units which extend throughout substantially the complete length of the press. Such drive units often comprise elongate drive chains which extend throughout the length of the press adjacent each side thereof, which chains are engaged by sprockets provided on the shifter housings to permit movement of the latter longitudinally along the press. To achieve synchronization between the drive units located on opposite sides of the press, some type of driving connection must be provided for extension transversely across the press, and this, coupled with the length of the chains extending along both sides of the press, make the overall structure mechanically complex and bulky, and hence expensive. Such drive structures are also subjected to significant exposure to chemicals and the like which may be in use in the surrounding environment, and hence such drive units have been observed to experience undesired chemical corrosion and the like.
Other automated shifter assemblies, in an attempt to eliminate elongate chains, have gone to so-called "rodless" pressure cylinders which are provided adjacent opposite sides of the press and movably supported on elongate guide rods which extend lengthwise throughout the press adjacent opposite sides thereof. These rodless cylinders, however, are themselves relatively expensive and can create undesired maintenance and repair. Further, it has been observed that using rodless cylinders adjacent opposite sides of the press, particularly in long presses employing large numbers of plates, can create operational problems in that it is significantly impossible to maintain proper control and synchronization over the rodless cylinders disposed on opposite sides of the press, and hence operation can cause sufficient nonsynchronous movement as to effect skewing of the plates so that the plate shifting operation can often become difficult to achieve.
Samples of typical plate shifting mechanisms which have been provided so as to permit more automated shifting of the plates are illustrated by U.S. Pat. Nos. 3,232,435, 3,251,472, 3,306,455, 3,331,511, 3,637,082, 3,712,460, 3,807,298, 4,295,970, 4,806,239 and 4,963,255.
Accordingly, it is an object of this invention to provide an improved plate shifting assembly for a filter press, which shifting assembly permits the filter plates to be automatically, sequentially and individually shifted into an open position when discharge of filter cake is desired, and which overcomes many of the disadvantages associated with automated shifting mechanisms of the type currently in use, as briefly described above.
More specifically, it is an object of this invention to provide an improved filter plate shifting assembly for a filter press, as aforesaid, which does not require use of elongate drive elements or mechanisms extending lengthwise throughout substantially the length of the press adjacent opposite sides thereof, but instead permits the drives to be entirely contained within small shifter housing parts which are positioned adjacent and traverses along opposite sides of the press frame.
It is a further object of the invention to provide an improved filter plate shifting assembly, as aforesaid, which when activated from a home storage position will readily traverse to a position for engagement with the endmost plate and will thereafter automatically and sequentially engage and move each endmost filter plate into an open position until all plates have been so moved, and whereupon the assembly will then automatically return to the home position and remain inactive until again activated for carrying out a further cake dumping operation.
It is still a further object of the invention to provide an improved filter plate shifting assembly, as aforesaid, which is compact, mechanically simple, and suitably protected from the environment to permit improved operating performance and efficiency.
It is also an object of the invention to provide an improved filter plate shifting assembly, as aforesaid, which is essentially self-contained in that the drive motors and all shifting drives including pressure cylinders and the like are all pneumatically driven and controlled so that only pressurized air need be supplied to the shifter housing, and the overall assembly is capable of carrying out the automatic and sequential moving of the filter plates solely under the control and actuation of air devices.
It is another object of the invention to provide an improved filter plate shifter assembly, as aforesaid, which permits the individual filter plates to be shifted in a manner whereby the shifting is sensitive to air pressure for terminating and reversing the shift mechanism drives, rather than being stroke sensitive, whereby the same mechanism can successively effect the desired automatic shifting of the plates even though the stack of plates in the press may include one more or less plate than is normally expected and which would prevent successful operation of a stroke sensitive shifting device.
In the filter press plate shifter assembly according to a preferred embodiment of the invention, there is provided a shifter housing having a tunnel-like center part which passes over the filter plates and has lower ends of the legs thereof provided with substantially closed housing parts which are positioned adjacent the opposite side rails of the press. These housing parts are rollingly supported on elongate support rods which extend along the press side rails for permitting the shifter housing to be moved longitudinally lengthwise of the press. One housing part has a rotary pneumatic motor mounted therein which drives a drive roller which is spring urged into driving engagement with the respective support rod. Each housing part mounts a plate shifter unit involving a pneumatic shift cylinder which is hinged at one end and provided with relatively fixed and movable plate shifting elements or blades at the other end. A pneumatic lift cylinder, when energized, pivots the shift cylinder upwardly so that the shift blades project into the space between the handles of adjacent plates, following which the shift cylinder is energized so that the movable blade engages the handle of the endmost plate and shifts the plate lengthwise of the press toward the open press head to permit discharge of cake from between the adjacent plates. When the plate effectively stops moving, either due to full extension of the shift cylinder or contact of the plate against another plate or against the movable head, then a pressure sensor retracts the shift cylinder and substantially simultaneously lowers the lift cylinder so that the shifter unit is in a position to initiate a new cycle. When in its original position, a further pressure signal again activates the drive motor to advance the housing to the next position for engagement with the next plate. The housing mounts thereon a plate sensing mechanism which engages and senses the leading plate in the stack and transmits a pressure signal for stopping the pneumatic drive motor. Each housing part also preferably mounts a pneumatically-actuated brake which is activated and engages the rod to hold the housing stationary when the motor is stopped.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.